Nonlocality of a Single Particle Demonstrated Without Objections

Nov 09, 2007 By Lisa Zyga feature
Nonlocality of a Single Particle Demonstrated Without Objections
Detecting single-particle nonlocality: The yellow path is Hardy’s original scheme. The red path is part of the modified version, where a reference state is created in the “black box.” The reference state is split off by beam splitter 1 toward Alice, and the other part is reflected off a mirror and then split off by beam splitter 2 toward Bob. This ensures that Alice and Bob can consistently compare their measurement results, and that the nonlocality must stem from the original single-particle state. (Modified image from Dunningham and Vedral)

Usually when physicists talk about nonlocality in quantum mechanics, they’re referring to the fact that two particles can have immediate effects on each other, even when separated by large distances. Einstein famously called the phenomena “spooky interaction at a distance” because information about a particle seems to be traveling faster than the speed of light, violating the laws of causality.

Although the idea is counterintuitive, nonlocality is now widely accepted by physicists, albeit almost exclusively for two-particle systems. So far, no experiment has sufficiently demonstrated the nonlocality of a single particle, although explanations have been proposed since 1991 (starting with Tan, Walls, and Collett).

Since then, the issue has been strongly debated by physicists. In 1994, Lucien Hardy proposed a modified scheme of Tan, Walls, and Collett’s claim. However, others (notably Greenberger, Horne, and Zeilinger) objected to Hardy’s scheme, claiming that it was really a multi-particle effect in disguise, and could not be demonstrated experimentally.

Now, Jacob Dunningham from the University of Leeds and Vlatko Vedral from the University of Leeds and the National University of Singapore have modified Hardy’s scheme, publishing their results in a recent issue of Physical Review Letters. By eliminating all unphysical inputs, their scheme allows for a real experiment, and ensures that only a single particle exhibits nonlocality. Plus, Dunningham and Vedral’s scheme not only applies to single photons, but to atoms and single massive particles, as well.

“The greatest significance of this work is that it shows how superposition and entanglement are the same ‘mystery,’” Dunningham explained to PhysOrg.com. “Feynman famously said that superposition is the only mystery in quantum mechanics, but more recently entanglement has been widely considered as an additional fundamental feature of quantum physics. Here we show that they are one and the same.”

In Hardy’s original scheme, one photon and a vacuum state arrive at a beam splitter, a glass prism that splits a beam of light in two. Two observers, Alice and Bob, have the option to either measure one of the beams, or to combine their beam with a coherent light beam, split the resulting beam with another beam splitter, and then measure the two outputs (also known as a “homodyne detection”).

Alice and Bob’s decisions could result in four possible combinations. First, if they both measure their beam from the original beam splitter, only one will detect a photon. Second, if Alice adds a coherent state to her beam while Bob measures his original split beam, Alice has two chances of detecting a photon, at the two outputs (c1, d1) of her beam splitter. Hardy showed that, if Alice detected a photon at c1, Bob would not detect a photon; but if Alice detected a photon at d1, Bob must detect a photon. In the third possibility, the roles of Alice and Bob are simply switched, with the same results.

In the fourth possibility, both Alice and Bob make homodyne detections. If they both detect particles at their d detectors (d1 and d2, respectively), then they both infer that the other must detect a photon from the original source. This is a problem, because they cannot both be right—there is only one original photon.

Hardy argued that this scheme demonstrates the nonlocality of a single particle when one eliminates the implicit local assumption that Alice’s result is independent of Bob’s measurement (and vice versa). Rather, one observer’s result does depend on the other’s measurement, so that, due to a nonlocal influence, the second observer’s measurement is determined by the first observer’s measurement.

“If we try and interpret this experimental scheme using only classical physics, it turns out that it is not possible for the outcomes of all four of the proposed experiments to be consistent,” Vedral explained. “The outcome of experiment four is not consistent with the others. Classical physics assumes that the particle exists independent of our observing (or measuring) it, and also that one measurement cannot influence a particle at a distance.

“For example, what Alice does cannot affect Bob’s particle,” he continued. “Since the outcomes of this scheme are not consistent with classical physics, we must drop one of the assumptions. This means that if we wish to maintain the view that reality exists independent of our measurements (e.g. the moon is there even if we don’t look at it), we are forced to accept that the world is nonlocal. This is how Hardy based his argument for nonlocality on the contradictory outcomes.”

However, Greenberger, Horne, and Zeilinger took issue with Hardy’s argument, pointing out that combining a photon and a vacuum does not result in an observable state, and therefore could not be performed in a real experiment. They even attempted a scheme that didn’t use these so-called “partlycle” superpositions, but found that the entire system then demonstrated nonlocality, making it impossible to attribute nonlocality to a single particle.

Dunningham and Vedral’s proposal makes a few key changes to Hardy’s scheme. First, instead of using coherent states of a photon and vacuum, they use mixed states—a mixture of coherent states averaged over all phases of the particles. In this way, they don’t violate superselection rules and so avoid objections that have been raised before.

Then, for the homodyne detections, they ensure that the coherent light beam combining with the original beam has the same phase. Having the same phase is key, as it ensures that Alice and Bob can consistently compare their measurement results. The coherent states are only classically correlated with the single particle state. This means that, when Alice and Bob perform their homodyne detections, and one detection influences the other, the nonlocality must stem from the original single-particle state.

Because the main importance is maintaining a common average phase—but not a specific phase—Dunningham and Vedral’s scheme could, in principle, be carried out in the laboratory. Also, the researchers suggest that, by using beam splitters for atoms and atom detectors, their scheme could conceivably verify the nonlocality of a single massive particle, in addition to a massless photon.

“An important feature of this work is that it shows how this experiment could be carried out without violating the number conservation superselection rule,” Dunningham said. “This is important because people are often happy to accept such violations for massless particles (e.g. photons) but not for massive particles such as atoms. By avoiding this violation altogether, we show that the outcomes of this proposed experiment should be the same for both massive and massless particles.”

The scientists note an interesting comparison of their result to a principle of Leibniz’s metaphysics, the identity of indiscernibles. According to the principle, a pair of entangled quantum particles must be indiscernible from a single particle, since both objects have in common all the same properties—this is the only stipulation of the principle, number being irrelevant. The single-state nonlocality demonstrated here reinforces the equivalence of a single state and an entangled state—giving more credence to the position that quantum field theory, where fields are fundamental and particles secondary, is a close representation of reality.

More information: Dunningham, Jacob and Vedral, Vlatko. “Nonlocality of a Single Particle.” Physical Review Letters 99, 180404 (2007).

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Researchers demonstrate ultra low-field nuclear magnetic resonance using Earth's magnetic field

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

User comments : 33

Adjust slider to filter visible comments by rank

Display comments: newest first

fluff
2.5 / 5 (4) Nov 09, 2007
Could this not be used as a radar system to detect stealth targets which rely on oblique scattering or absorption? Their system does not rely on receiving the photon back, just knowing whether one of the beams has been intercepted(detected) before the other beam (kept confined at receiver) - this can be done at a range of time intervals to get range to go with the direction. Please point out my wrong assumptions (if any :)
earls
1 / 5 (4) Nov 09, 2007
So. Superluminal communication = confirmed?
holoman
1 / 5 (7) Nov 09, 2007
This silly little experiment proves nothing about quantum particle entanglement and yes entanglement is superluminal.
earls
1.9 / 5 (8) Nov 09, 2007
If I had two entangled tennis balls sitting on the floor and I pick one up, the other will also rise?
LearmSceince
4.2 / 5 (5) Nov 09, 2007
[quote=holoman]This silly little experiment proves nothing about quantum particle entanglement and yes entanglement is superluminal.
[/quote]
That silly little comment illustrates a profound lack of understanding of quantum physics.

[quote=earls]If I had two entangled tennis balls sitting on the floor and I pick one up, the other will also rise? [/quote]

No. Changing one particle does not cause a change in the other. Observing the particle tells you something about the other: if you knew that both balls were in the same court, then saw one of them, you would know the other one was also in this court. Very underwhelming, until you get into conjoined variables.
LearmSceince
4 / 5 (4) Nov 09, 2007
Could this not be used as a radar system to detect stealth targets which rely on oblique scattering or absorption?


No, but see the Elitzur-Vaidman bomb-testing problem for the configuration you are thinking of.
earls
1.3 / 5 (3) Nov 09, 2007
"Changing one particle does not cause a change in the other."

As this would violate causality?
earls
1 / 5 (5) Nov 09, 2007
Also, if this research is so worthless, why is there so much research into it? For the sake of just knowing?
fredrick
3.4 / 5 (5) Nov 10, 2007
Duh, learm, the concept of entanglement is one particle does effect the another.


If two particles are entangled, changing one doesn't mean that there will be a change in the other. The entangled particles are in superposition until they are observed, and upon observing one of these particles it will no longer be in superposition - it will have a definite state with certain measurable variables which can also tell you about the state of the other particle.
So, for example, there is some atom that decays which we know will result in two particles being made. We also know that one of these particles must be spin-up, and the other must have be spin-down. They are in superposition until observed (or however you want to interpret it, it really doesn't matter all that much), thus for all we know, upon observation particle A or B might be either spin-up or spin-down. Upon observation of particle A, we see that it is spin-up. Thus, we know that particle B is spin-down. If we are going along with the interpretation I'm using, this means that the observation-initiated wave-function collapse of particle A instantaneously causes a wave-function collapse of particle B.

If nothing else, you can take it to mean that while it was impossible to predict particle B's properties before particle A's observation, suddenly after observing particle A we are able to reliably predict particle B's properties. The famous EPR paradox (although commonly described otherwise) is when one tries to use this knowledge gained of the other particle in trying to measure pairs of mutually exclusive observables (ie, the Uncertainty principle doesn't allow that we will find a definite value for spin along the x, y and z axis - if we know spin along the x-axis is up, then along the z-axis is undefined). Try in one place to measure spin on x-axis on particle A and you will know what it is on particle B; and at the same time elsewhere measure spin on y-axis on particle B, and thus you will have knowledge of the x and y-axis spins on both particles, which contradicts the HUP. The universe doesn't let you do this, though, and so we get "spooky action at a distance" - by measuring along the x-axis on particle A, instantaneously across any amount of space particle B will be put in a state of ill-defined spin on the y-axis.



So, moving particle A to the left *doesn't* mean that particle B will suddenly move to the left too. That is not quantum entanglement. Thus, Learmscience's answer to earls regarding picking up tennis balls was correct, and once again you are demonstrating that your "silly little comment illustrates a profound lack of understanding of quantum physics"

Duh, learm, balls in a court ? what does that have to do with entanbled particles, is this some insane method or maddess that leads to some bizzare understanding of what I don't know,,,,, but I sure its perfect in your absurd mind.


Learm didn't first mention the balls in the court - that was earls. Learm was making a reply to earls. Duh.
blacker
1 / 5 (6) Nov 10, 2007
Nonlocality proves that the universe is within one mind that all who are aware, share awareness through.
holoman
1.8 / 5 (5) Nov 10, 2007
Fredrick,

In quantum mechanics, all the forces of nature are mediated by the exchange of particles such as photons, and these particles must obey this cosmic speed limit. So an action "here" can cause no effect "over there" any sooner than it would take light to travel there in a vacuum.


But two entangled particles can appear to influence one another instantaneously, whether they're in the same room or at opposite ends of the Universe.


Einstein called this %u2018spooky action at a distance%u2019 - spooky because there is no known mechanism for such an interaction, and because it would entail that things can be affected by events which, in some frame of reference, haven't happened yet.


Quantum entanglement occurs when two or more particles interact in a way that causes their fates to become linked: It becomes impossible to consider (or mathematically describe) each particle's condition independently of the others'. Collectively they constitute a single quantum state.


Austrian physicist Erwin Schrödinger in 1925 showed that if two particles are prepared in a quantum state such that there is a matching correlation between two %u2018canonically conjugate%u2019 dynamical quantities %u2014 quantities like position and momentum whose values suffice to specify all the properties of a classical system %u2014 then there are infinitely many dynamical quantities of the two particles for which there exist similar matching correlations: every function of the canonically conjugate pair of the first particle matches with the same function of the canonically conjugate pair of the second particle.


Thus system No. 1 %u2018does not only know these two answers but a vast number of others, and that with no mnemotechnical help whatsoever, at least with none that we know of.%u2019


Schrödinger coined the term %u2018entanglement%u2019 to describe this peculiar connection between quantum systems:


When two systems, of which we know the states by their respective representatives, enter into temporary physical interaction due to known forces between them, and when after a time of mutual influence the systems separate again, then they can no longer be described in the same way as before by endowing each of them with a representative of its own. I would not call that one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought. By the interaction the two representatives [the quantum states] have become entangled.


Entangled Particles will be the name given to this hallmark discovery in which the event history of entangled particles is continuously emitted (broadcast) non-locally and is received by and interacts with the other entangled particle pair's matter in its environment through a subtle process of exchange of quantum information. This is an extension of the known process of quantum emission/absorption and analogous to non-local quantum entanglement of the particle pairs matter.


Entangled Particle extends the reach of quantum physics beyond the atom and subatomic particles, not only deeper into the quantum state, but also into the larger world of encrypted particle transmission. It brings the role of information in physical theories to the same level of importance as energy itself. Entangled Particle focuses not so much on particles as on the relationships and dynamic exchanges between energy, matter, photons, electric fields, and information. Entangled Particle looks into four basic quantum processes, heretofore largely ignored and left unexplored by science. They are as follows:


Entanglement:


The state or condition in which an enduring confluence occurs between atomic and subatomic particles during energy exchange or other processes, characterized by a commingling of particle attributes, such as spin, EMF, and quantum energy of shared interchange electrons in a persistent and congruent manner. Associated with entanglement is an instantaneous non-local, exchange of information through the use of a particle medium for quantum correlation.


Coherence/Quantum Interference Correlation:


The observation made under experimental conditions that paired particles do not move or behave independently when involved in the same process or in energy transfers, as predicted by classical theory, but rather amalgamate in a sustained fashion and remain enjoined as an enduring discrete ensemble of particles with compatible spin and polarization characteristics, regardless of what paths, vectors or trajectories are adopted subsequently.

Non-Locality (near & far):


The omnipresent and omnidirectional transfer of influence at the quantum level instantly, simultaneously and ubiquitously, through wave-like or field-like resonance wherein spatial and temporal factors are inconsequential.


Interconnectedness:


The state of a universe that is considered to be unified and joined together holistically, through a process of non-local resonance occurring within the underlying zero-point field, that connects all matter, energy and information in the cosmos.


Entangled Particles suggests that all things in the universe are interconnected informationally. It also maintains that underlying this unity or oneness is the mystifying and mysterious dance between all matter and energy and information. Simply put, the basic promise of Entangled Particle is that the most profound insights about our universe will be discovered among the most subtle, implicit, and invisible phenomena of the sub-quantum level.

One is about an effect of quantum mechanics that is not comparable with any phenomenon of the worlds current dimensions, since the two pair entangled photons, working in opposing directions, remain entangled between themselves.

I will now make sure your name is entangled with LearmScience so there are no misapprehensions on who is who and what is what from you both,i.e., another mysterious effect in the universe. Duh.

earls
1 / 5 (3) Nov 10, 2007
[citation needed]
fredrick
3 / 5 (4) Nov 10, 2007
holoman, your copy paste skills are amazing. Thank you, BTW, for writing a bunch of stuff I already knew (and in fact, already said), and a bunch of stuff which I would argue but its really off-topic so i wont bother. Simply: are you suggesting that entanglement is when, if two particles are entangled, then moving one particle upwards will also cause the other to move upwards?
earls
3 / 5 (2) Nov 11, 2007
"To build a working quantum computer, the atoms that make up these qubits must be "entangled" - inextricably linked so that making a change to one qubit instantaneously alters the quantum state of its partner."

Wait.

"Changing one particle does not cause a change in the other."

What am I missing?
atulK
2.5 / 5 (2) Nov 12, 2007
guys I am pleased to see that Quantum nerds argue the same way as street fighters. :)

Well, my Q is - isn't observation same as changing something for that particle, atleast in QM? so why were there arguments about - it's just observation, not changing - (you) dude types?
atulK
1 / 5 (2) Nov 12, 2007
guys I am pleased to see that Quantum nerds argue the same way as street fighters. :)

Well, my Q is - isn't observation same as changing something for that particle, atleast in QM? so why were there arguments about - it's just observation, not changing - (you) dude types?
C_Ell
not rated yet Nov 12, 2007
I'm perplexed that they mention Tan and Hardy, but not Hessmo et al (Phys. Rev. Lett. 92, 180401 (2004)). There was even a Phys Rev Focus article on that paper.
Ragtime
1.8 / 5 (4) Nov 12, 2007
The nonlocality is quite common phenomena in dense particle system, like the dropplets inside of condensing supercritical vapor, which can be considered as a classical mechanics model of vacuum. These fluctuations are behaving like undulating dropplets, which we can imagine as an undulating oily dropplets inside of lava lamp with very low dumping of surface undullations.

When such undulating dropplets will be broken into two parts, their surface undulations don't dissapear, they'll remain undulating at the phase, instead. The ocassional reconection will recover the surface undulations of the original dropplet in its previous state, so we can say, these dropplets are entangled mechanically.

Note that even if the frequency/amplitude of the surface undulations of all fragments will remain the very same, the randomly choosen pair will not recover the previous dynamic state of the original dropplet, until the surface undulations will not remain exactly of the same phase. The phase of surface wave with respect of center of mass of both dropplets will serve here as an "hidden memory" and/or "hidden variable". By such way, the center of common mass serves as a local reference frame for surface energy spreading, i.e. it's forming a local multiverse, whose phase is retained even if both the dropplets will remain separated to arbitrary distance. Therefore, the dropplet model can serve as an trivial illustrative model of entanglement and decoherence phenomena.
fredrick
2.3 / 5 (3) Nov 12, 2007
Well, my Q is - isn't observation same as changing something for that particle, atleast in QM? so why were there arguments about - it's just observation, not changing - (you) dude types?



which is what I'm guessing earls' quote was referring to. One can, if they want to, constrain the possible temporal evolutions of an entangled particle by making certain decisions about how to observe the other particle. As (I think it was) Schrodinger put it, one can "steer" the way entangled particle-B will be measured by the way they measure particle-A.
The wave-function of each particle is dependent on the wave-function of the other, which is what 'entanglement' is - when, after some interaction, two seperate things can no longer be described sufficiently in seperation from each other. In order to describe the system, we need to describe both A and B in unison, we can't describe each seperately.

I was, in fact, about to say that myself, right after I finished commenting on the crazy creationists in the other news. The reason why I didn't mention it in the first comment is because we are talking two different types of 'change' here.

(1) 'Change' as in, we are constricting the wave-function of B by our actions on A, thus constricting the possible states into which it might collapse upon observation.

and

(2) moving A some direction, causing B to move in the same direction.


The tennis ball example, to which I was replying, was (2): "if I pick up an entangled tennis ball, will the other rise as well?". That type of 'change' is very different from the type of 'change' that occurs with quantum entanglement.

Well, my Q is - isn't observation same as changing something for that particle, atleast in QM? so why were there arguments about - it's just observation, not changing - (you) dude types?


I suppose that could depend on your interpretation. In many-worlds, for example, you don't change the thing by observing it (not including the observer-effect). In Copenhagen, I'm not sure if you can be said to have 'changed' it... the thing was in superposition and observation brings it out of superposition, if you want to call that change.
LearmSceince
5 / 5 (1) Nov 14, 2007
holoman, your copy paste skills are amazing.
...
Simply: are you suggesting that entanglement is when, if two particles are entangled, then moving one particle upwards will also cause the other to move upwards?


One of the frames in his animated GIF on his site (here) indicates that he believes exactly that. He has instant communication by having one computer read a qbit, mistakingly thinking that he can force the state and provide superluminal communication.

LearmSceince
not rated yet Nov 14, 2007
earls ponders, "...so that making a change to one qubit instantaneously alters the quantum state of its partner."

Wait.

"Changing one particle does not cause a change in the other."

What am I missing?


The "change" that takes place is random! Two people measuring their stream entangled bits will each see a list of random numbers. Only when they get together and compare notes will they see that they got the [I]same[/I] random numbers. A performs a measurement and gets a random result. B measures the twin and gets the same result. B knows what A got, but A cannot send a purposeful message to B.
fredrick
1 / 5 (2) Nov 15, 2007
One of the frames in his animated GIF on his site (here) indicates that he believes exactly that. He has instant communication by having one computer read a qbit, mistakingly thinking that he can force the state and provide superluminal communication.



bahahaha... that was funny. I've been wondering how serious that site is (tl;dr myself, been busy), especially after another post where he claimed a few patented technologies which were... far fetched, to put it nicely.
Weir
1 / 5 (1) Nov 15, 2007
The Non-locality of a single particle confirms that physical matter has both universal and particular aspects. An atom is the intimate coherence of these two fundamental characteristics common to all physical phenomena. This is not consistent with causality associated with the continuous field concept in the physical sense of matter imbedded in a spacetime continuum. Einstein himself questioned the continuum basis of his own work late in life. In a discontinuous universe a different picture emerges that is consistent with the evidence and with common sense.

Planck's constant indicates a discontinuity in the synchronous projection of particulate matter. The electromagnetic rainbow is sliced across it entire breadth. EM radiation comes to us as a discontinuous series of pulses. The universal component of atoms regulates their synchronous projection in a series of independent still space frames linked up by light. All relative motion comes as quantum jumps between these discrete still particle frames. Light is the only activity within each space frame. It is quantized by each space frame. Light comes from inside atoms and has a universal relationship to each atom, accounting for its universal velocity. Light itself defines space. Where there is no light, there is no space. And obviously physical effects can not be transmitted through the integrated fabric of space-time faster than light. But space frames are discontinuously assimilated from the timeless quantum frame by the universal characteristic of matter and so sub-atomic particles remain implicitly and timelessly correlated. So do all atoms. All physical particle action takes place via the holistically integrated quantum frame, called the Void.

More at www.cosmic-mindreach.com.
fredrick
1.5 / 5 (2) Nov 15, 2007
The "change" that takes place is random! Two people measuring their stream entangled bits will each see a list of random numbers. Only when they get together and compare notes will they see that they got the [I]same[/I] random numbers. A performs a measurement and gets a random result. B measures the twin and gets the same result. B knows what A got, but A cannot send a purposeful message to B.



with a preestablished code of sorts (kinda like, "if you get x it means that i've measured for y, which means z"), one *could* send a message through entanglement... but the kind of instant messaging system like in holoman's .gif, or in the tennis ball example, doesn't happen.
earls
1 / 5 (1) Nov 16, 2007
Not yet.
fredrick
1 / 5 (2) Nov 16, 2007
Well, if the tennis ball thing ever does happen, it won't be through quantum entanglement. Or at least, it won't be through quantum entanglement acting alone, there would have to be some other mechanism to lift the balls. (BTW, position and momentum are one of the pairs of observables that cannot be observed together in detail - so at the quantum scale, I know for sure that so long as the HUP is correct, moving A isn't going to cause an equal move in B elsewhere)
LearmSceince
not rated yet Nov 19, 2007
One of the frames in his animated GIF on his site (here) indicates that he believes exactly that. He has instant communication by having one computer read a qbit, mistakingly thinking that he can force the state and provide superluminal communication.


bahahaha... that was funny. I've been wondering how serious that site is (tl;dr myself, been busy), especially after another post where he claimed a few patented technologies which were... far fetched, to put it nicely.


Just search for 'holoman' as author on the forum here. (before this current system, news feedback was done with forum topics) Any article mentioning quantum stuff, he posts to say "sorr, too late! I already did that." Although most of his page sounds like a good sci-fi backstory, some of it, like the GIF slide, are real wammies. And he's never fixed it after being told many times.
LearmSceince
5 / 5 (1) Nov 19, 2007
with a preestablished code of sorts (kinda like, "if you get x it means that i've measured for y, which means z"), one *could* send a message through entanglement... but the kind of instant messaging system like in holoman's .gif, or in the tennis ball example, doesn't happen.


That's not considered "communication". But it does provide for synchronization. Another way which shows the same issue is to have both people (here an near Tau Ceti) both watching a quazar that just happens to be the same distance from both, billions of light years away. The particular hiccups in X-ray brightness can be used to synchronize their actions, as each knows what the other intends to do based on that signal.
fredrick
1 / 5 (2) Nov 20, 2007
perhaps its not considered 'communication', but couldn't we still consider it 'sending a message'?
earls
1 / 5 (1) Nov 20, 2007
lol. You're going to split hairs on the definitions of "communication" and "sending a message?" Look, either it is or isn't, will or won't be. Which is it?
LearmSceince
not rated yet Nov 21, 2007
perhaps its not considered 'communication', but couldn't we still consider it 'sending a message'?


No. It cannot potentiate a cause/effect relationship between the two ends. Playing a pre-arranged script based on a signal from a 3rd party does not constitute communication. The interesting things concerning what is summarized by the term "communication" has to do with causality, and with mass/energy transfer. Pre-arrangement doesn't do anything like that.
I'm not splitting hairs. It is fundamental to what is interesting about the physics.
LearmSceince
not rated yet Nov 21, 2007
(kinda like, "if you get x it means that i've measured for y, which means z"),


If you get x, you still don't know what I measured for. You know that IF I measured for the same variable, I'll have gotten -x. But I may have measured for the other variable, and you still got x. In fact, what variable I measured for does not change the probability of you getting x when you make your measurement!
Han
1 / 5 (1) Nov 28, 2007
Perhaps it has been asked before, but originally in the experiment of Aspect c.s. there was entanglement of photon polarization. What is entangled here? Is there an entanglement between photon polarization and vacuum?